DevTools: Cache the original content on UISourceCode

third_party/WebKit/Source/devtools/front_end/bindings/ContentProviderBasedProject.js

Index: third_party/WebKit/Source/devtools/front_end/bindings/ContentProviderBasedProject.js
diff --git a/third_party/WebKit/Source/devtools/front_end/bindings/ContentProviderBasedProject.js b/third_party/WebKit/Source/devtools/front_end/bindings/ContentProviderBasedProject.js
index 3e5a1ea1a1a299a8b065acd022c9db77d0e63ffd..140475424f431fcd6a7aacf68c19d6a56435e123 100644
--- a/third_party/WebKit/Source/devtools/front_end/bindings/ContentProviderBasedProject.js
+++ b/third_party/WebKit/Source/devtools/front_end/bindings/ContentProviderBasedProject.js
@@ -60,6 +60,18 @@ Bindings.ContentProviderBasedProject = class extends Workspace.ProjectStore {
 
   /**
    * @override
+   * @param {!Workspace.UISourceCode} uiSourceCode
+   * @return {!Promise<?string>}
+   */
+  requestOriginalFileContent(uiSourceCode) {
+    var fulfill;
+    var promise = new Promise(x => fulfill = x);
+    this.requestFileContent(uiSourceCode, fulfill);
+    return promise;
+  }
+
+  /**
+   * @override
    * @return {boolean}
    */
   isServiceProject() {
@@ -87,10 +99,10 @@ Bindings.ContentProviderBasedProject = class extends Workspace.ProjectStore {
    * @override
    * @param {!Workspace.UISourceCode} uiSourceCode
    * @param {string} newContent
-   * @param {function(?string)} callback
+   * @param {function()} callback
    */
   setFileContent(uiSourceCode, newContent, callback) {
-    callback(null);
+    callback();
   }
 
   /**